HIDDEN, FOUETH AND SMALLER GLACIERS 15S these sites was on a low knoll, about 200 feet above the sea, and very near the outer edge of the outwash gravel plain. In the picture of July 26, 1905, from this site the glacier front is distant and ice occupies only a very small fraction of the entire picture, all the foreground for two miles being outwash gravel plain. In the picture of July 10, 1909, from the same site, on the other hand, the glacier dominates the view (PL LXXIX, A), and the outwash gravel plain occupies only a narrow strip. Between two and three-square miles of ice, with an average depth of several hundred feet, has been added in this picture. No less striking is the difference in appearance of the Hidden Glacier valley in the two photographs from the same site on the alluvial fan at the outermost part of the outwash gravel plain, one taken July 6, 1906 (PI. LXXX, A), and the other July 10, 1909. In the latter picture the ice front is near at hand and the glacier is so large that it was impossible to show it on a single 5x7 plate, whereas in the 1906 photograph the glacier front extends only about a fourth of the way across the picture. Such a sudden and enormous change in the position of the glacier front in so brief a • time is, so far as we know, without recorded parallel. Accustomed as we were by this time to such transformations of glaciers, the change in the Hidden Glacier seemed to us; almost incredible, even as we looked upon it with our own earlier photographs in our hands. The surface of the glacier contrasted as strikingly with its 1905 condition as did the position of its front. From the very outer edge, back as far as we could see up the glacier valley, and from one side to the other, the ice surface was rough and broken, forming a striking contrast to the smooth, unbroken surface of 1899, 1905, and 1906. The roughness, though great, was not of the same character as that presented by the Atrevida, Variegated, Haenke, and Marvine Glaciers in 1906, and by the Lucia Glacier in 1909. In these cases the ice was so broken, there were so many pinnacles, and such a mass of yawning crevasses, that the glaciers were impassable; but in the Hidden Glacier the irregularities were all rounded (PL LXXXI) and it is clear that there had been not only a breaking of the surface, but, as in the case of the Variegated Glacier in its 1909 condition, a subsequent healing as well. Although exceedingly rough, and with numerous crevasses, it seemed to us from the view which we obtained on the north side at an elevation of 600 feet, where we could look over the broken surface, that it would be possible to traverse it in almost any part, though there were areas of excessive crevassing which would undoubtedly make necessary the exercise of great care. We walked over portions of the northern margin and the lower end of the glacier in order to satisfy ourselves as to the exact conditions from near at hand, and what was observed there seemed to be a duplication of the conditions throughout most of the visible glacier surface. These parts of the glacier surface were made up of a series of huge swells, with somewhat sharpened crests, rising from 20 to 50 feet above the broad depressions between them and giving to the surface an undulation strikingly in contrast with the regularity and smoothness in 1905. Everywhere along the margin of the glacier, the ice was badly cracked and seamed, showing the great strain to which it has been subjected; and, in addition, the surface was interrupted by innumerable crevasses, some of them of considerable depth, so that in crossing the glacier it was necessary to follow a winding path in order to avoid the crevasses. Everywhere ablation was in rapid progress and many streams were coursing over the glacier surface, which had almost no morainic veneer to protect it from melting.